Modern high horsepower tractors enable the use of wide swath implements. For example, field sprayers are presently being constructed with spray booms that will extend to more than 100 feet. Such frames, are designed to fold behind the towing vehicle in order to enable transport along roadways. This process typically involves a substantial amount of time and manual effort on the part of the operator.
U.S. Pat. No. 4,739,930 to Pask discloses an agricultural field sprayer that includes a folding boom frame. Opposed "wings" of the boom frame fold between field operative positions and rearwardly extending positions for roadway transport. A rigid pull bar or brace member connects the central tongue spray boom frames. In the operative field position the pull bar lends structural stability to the laterally outward extending boom sections. The pull bar, described as a "draw", is secured between the boom section, a tongue frame, and a fold arm. The fold arm is used to support the "draw" as the boom sections are pivoted from the operative, to the inoperative, transport condition. The fold arms themselves project laterally outward when the boom sections are pivoted back to their transport condition. In order to enable roadway transport, the fold arms must be disconnected from the "draws" and manually folded, along with the "draws" to a narrower transport condition. This process involves significant manual manipulation by the operator and, consequently, takes a considerable amount of time. The same is true for setting the apparatus up to be pivoted to its field condition.
U.S. Pat. No. 4,821,809 to Summach et. al. discloses a multiple section draw bar that, like the Pask patent above, folds between a laterally extending operative condition, and a rearwardly folded transport condition. This apparatus makes use of a flexible guy wire or "stay" that is secured between the tongue frame and outwardly extending boom sections in their operative conditions. To facilitate pivotal motion of the sections to their folded, transport conditions, the stays must be disconnected and stored.
Relatively rigid pull bar members interconnecting folding boom sections and a tongue frames are desirable to stabilize the long, outwardly extending boom sections. Still, a need has remained for a folding implement frame with a rigid pull bar that may be substantially automatically pivoted between outwardly extending operative and inwardly folded transport conditions.